Why is the risk of heart failure higher during or after pregnancy?

Heart failure related to pregnancy is rare and usually caused by peripartum cardiomyopathy. In this disease, the heart cannot pump blood with enough force because the muscle of the pumping chambers has stretched (dilated) too much and become weak. No one knows what causes peripartum cardiomyopathy, but it affects previously healthy women in whom the heart becomes weakened during the last month of pregnancy or up to 5 months after delivery.

Women with congenital heart defects (structural abnormalities of the heart that are present at birth) may also be at risk for developing heart failure during or after pregnancy. Pregnancy and childbirth place added stress on the heart, as it has to work harder to pump about 30% to 50% more blood than normal to supply oxygen to the fetus. These stressful changes in blood flow may not be well tolerated by women with certain congenital heart defects.

How common is heart failure during or after pregnancy?

Heart failure related to pregnancy is rare, and little is known about how many pregnant women have heart failure. Peripartum cardiomyopathy affects only 1 in every 3000 to 4000 deliveries in the US. It is more common in women who have high blood pressure, multiple pregnancies, and multiple births, and in women who are older or African American or who have been given medication to prevent premature delivery.

Heart failure during pregnancy is also more common in women with inborn heart defects (congenital heart defects). However, not all congenital heart defects pose an increased risk of developing heart failure in pregnant women. A review of nearly 2500 pregnancies observed that heart failure occurred in about 5% of women with congenital heart defects, primarily in women with more complex and severe heart defects.

How can I prevent pregnancy-related heart failure?

The best strategy to minimize your risk of heart failure is to work with your health care practitioner to address the major risk factors that are under your control: high blood pressure, diabetes, obesity, and heart disease. Women with high blood pressure who are planning to become pregnant should talk to their doctor about proper precautions to take before conceiving, such as controlling their blood pressure and weight.

If you are a woman born with a heart defect, you need to discuss the risks associated with pregnancy with your cardiologist (heart specialist). Your risk will depend on the size and severity of your heart defect and if you are on medication or have had surgery. Most women with congenital heart defects had surgery in childhood, making it possible for them to grow as normally as possible. Surgery, however, does not mean the heart is normal; additional heart problems may develop in adulthood, especially if a pacemaker or a valve replacement was implanted.

What is my outlook if I have pregnancy-related heart failure?

Women with peripartum cardiomyopathy are usually treated aggressively with medications and lifestyle changes. More than half of all women recover completely. However, women whose hearts do not fully recover after peripartum cardiomyopathy risk serious problems, including death, with their next pregnancy. A study of the next pregnancies in 44 women who had previously suffered peripartum cardiomyopathy found that a quarter of the women who had not fully recovered had to terminate their following pregnancy to save their own lives, about half developed heart failure, and 19% died. Women whose hearts did make a full recovery before they became pregnant again fared better. Women who have had peripartum cardiomyopathy should discuss with their doctor any future plans to become pregnant and the need to discontinue certain drugs that may cause birth defects if taken while pregnant, such as ACE inhibitors.